(1) Field of the Invention
This invention relates to a reflector for a linear light source and to a louvre controller including a reflector.
(2) Description of the Related Art
Linear light sources, for example linear fluorescent lamps, are known which use a louvre controller having profiled side reflectors and transverse reflectors.
A perspective top view of a known louvre controller is shown in FIG. 1, having opposed generally arcuate side reflectors 10, 11, which extend parallel to an axial direction indicated by arrow headed line 12, of a linear light source 21. Disposed in a transverse direction (as shown by arrow headed line 13) are plural profile transverse reflectors 14, ten such transverse reflectors being shown in the exemplary embodiment of FIG. 1. It is to be understood that fewer or more transverse reflectors 14 may be provided in dependence upon the length of the linear light source.
A perspective underside view of a single known transverse reflector is shown in FIG. 2. The transverse reflector, shown in FIG. 2, is formed from a folded sheet of metal and has two opposed generally arcuate side surfaces 16, 17, the fold between the surfaces 16, 17 forming a straight knife edge 18. An upper portion of each of the side surfaces 16, 17 is relieved with a V-shaped groove 19, 20 for accommodating the linear light source 21.
The geometry of the louvre controller is determined so as to limit the intensity of light beyond required angles and the limitation is created by providing cut-off angles to prevent direct light from the light source being viewed.
FIG. 3 shows a diagrammatic end view of a louvre controller in which the side reflectors 10, 11 create a cut-off angle A in a transverse direction from the linear light source 21.
FIG. 4 shows, in diagrammatic form, a side view of a louvre controller in which the transverse reflectors 14 create a cut-off angle B in the axial direction. The angles A and B may be the same or different to one another.
It is, however, also necessary to control the intensity of light through all angles of azimuth, i.e. through 360° of the horizontal plane. In order to achieve such a function, the transverse reflectors are moved closer together to limit the direct light between the transverse and axial directions. In other words, the spacing, or pitch P, between the transverse reflectors is reduced.
For clarity, the horizontal plane showing 360° of azimuth is shown in a top plan view of FIG. 5 where the angles of azimuth are referenced 25. FIG. 6 shows a side view of a louvre controller which is helpful in understanding cut-off angles in which the vertical cut-off angle C is shown and the azimuthal volume described thereby, in which there is to be no direct view of the linear light source (shown by cross-hatched lines 26).
From the foregoing it will be understood it is necessary to provide cut-off angles not only in the axial 12 and transverse 13 directions, but also for vertical cut-off angles C for horizontal azimuthal angles 25.
Because the transverse reflector pitch P is necessarily reduced to achieve cut-off in axial, transverse and azimuth directions, the number of transverse reflectors along the axial length of the linear light source is increased. The transverse reflectors, although useful in the control of light, also create obstructions and, therefore, reduce the light output of the louvre controller. This reduction in light output is termed as a loss in light output ratio (LOR).